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为什么没有检测到这个变量?安卓工作室Kotlin

android-bluetooth kotlin android

Incog · 技术社区 · 1 年前

在下面的代码中,无法识别“takePermission”和“bluetoothAdapter”。我一直在关注 this tutorial 这似乎有点过时,但他的变量被公认为没有问题。

class MainActivity : ComponentActivity() {
    lateinit var bluetoothManager: BluetoothManager
    lateinit var bluetoothAdapter: BluetoothAdapter
    lateinit var takePermission: ActivityResultLauncher<String>
    lateinit var takeResultLauncher: ActivityResultLauncher<Intent>
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        bluetoothManager = getSystemService(BLUETOOTH_SERVICE) as BluetoothManager
        bluetoothAdapter = bluetoothManager.adapter
        takePermission = registerForActivityResult(ActivityResultContracts.RequestPermission()){
            if (it){
                val intent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
                takeResultLauncher.launch(intent)
            } else {
                Toast.makeText(applicationContext,"Bluetooth Permission not given",Toast.LENGTH_SHORT).show()
            }
        }
...

@Composable
fun Greeting() {
    Column(
        modifier = Modifier.fillMaxWidth(),
        horizontalAlignment = Alignment.CenterHorizontally,
        verticalArrangement = Arrangement.Center
    ) {
        Text("Bluetooth ON/OFF Application", fontSize = 20.sp,
            fontWeight = FontWeight.Bold, textAlign = TextAlign.Center)
        Spacer(modifier = Modifier.height(20.dp))
        OutlinedButton(onClick = {
            takePermission.launch(android.Manifest.permission.BLUETOOTH_CONNECT) //unresolved reference error
        }) {
            Text("Bluetooth On", fontSize = 30.sp,
                fontWeight = FontWeight.Bold)
        }
        Spacer(modifier = Modifier.height(20.dp))
        OutlinedButton(onClick = {
            bluetoothAdapter.disable() //unresolved reference error
        }) {
            Text("Bluetooth Off", fontSize = 30.sp,
                fontWeight = FontWeight.Bold)
        }
        Spacer(modifier = Modifier.height(20.dp))
    }
}

1 回复 | 直到 1 年前

selbie 1 年前

在黑暗中拍摄,根据观察到的凹痕图案进行猜测。缩进模式表明 Greeting 实际上不在MainActivity的类范围内。即你有 招呼 作为一个全局函数。

我怀疑您的代码结构是这样的:

class MainActivity : ComponentActivity() {
    lateinit var bluetoothManager: BluetoothManager
    lateinit var bluetoothAdapter: BluetoothAdapter
    lateinit var takePermission: ActivityResultLauncher<String>
    lateinit var takeResultLauncher: ActivityResultLauncher<Intent>

    override fun onCreate(savedInstanceState: Bundle?) {
    }

    ...

}  // END OF MainActivity Defintition


// Greeting is at global scope
fun Greeting() {

}

您想要:

class MainActivity : ComponentActivity() {
    lateinit var bluetoothManager: BluetoothManager
    lateinit var bluetoothAdapter: BluetoothAdapter
    lateinit var takePermission: ActivityResultLauncher<String>
    lateinit var takeResultLauncher: ActivityResultLauncher<Intent>

    override fun onCreate(savedInstanceState: Bundle?) {
    }

    fun Greeting() {

    }

}  // END OF MainActivity Defintition

如果这不能解决你的问题,那么我怀疑你需要发布 MVCE .